Design of a Mushroom Farm/Spawn Lab (2024)

1. The Overall Design of the Farm / Lab

The fruiting room and the inoculation room are at the center of the farm / lab design but are not the only components. We’ll see first the mushroom farm design overview and components, then details about the inoculation room and fruiting room design.As an example of small scale urban farm, seemy article about our two setupsandmy video of our first setup.

For the design of our mushroom farm, I found very precious the instructions fromPaul Stamets books “Growing Gourmet and Medicinal Mushrooms”and“The Mushroom Cultivator”, Specifically, Appendix Ifor mushroom farm design overview,Appendix IIfor spawn lab design, Appendix IIIfor fruiting chamber design. These 25 pages may seem overwhelming at first, but there is a great amount of detail about the setup and materials well needed if you are building one, I’ll summarize here.

The setup is in two complexes, ideally in separate buildings. If you are building a small scale farm, you may not need all the mentioned spaces, just the essentials (in bold).

• The grow room complex including :
  • • Fruiting room(s),
  • • Inoculation room,
  • • Pasteurization room,
  • • Main corridor,
  • • Packing room,
  • • Refrigeration room,
  • • Shipping & Receiving room and
    • Production/Recapture Open-Air Growing space

• The laboratory complex, from P464 :
  • • Sterile inoculation room,
  • • Incubation rooms for spawn and sawdust bags,
  • • Microscopy Media room,
  • • Dress-down/ cleanup anteroom to sterile room,
  • • Boiler room,
  • • Grain storage room,
    • Office, etc.

These spaces are articulated in an overall design that optimize sterility and substrate circulation. Mushroom farming benefit from space compartmentalization, that allows the application of few useful design idea, such as:

• Three doors from outdoor to HEPA flow: Stamets recommends having three doors to cross to reach the flow hood room from the outdoor air. This can be integrated in the farm design, e.g. by using an incubation room as an ante-room.

• Separate inoculation and fructification:inoculation is the main source of contaminants in mushroom farming. Stamets recommends separate building for spawn lab and growing room.When possible I would also place pasteurization, inoculation, incubation of pasteurized bag away from the fruiting room.
• Exploit airflow :Stamets recommends a hepa filtered positive pressured lab. This filtered clean air can be recycled in the incubation room, and then in the preparation space, creating a continuous flow opposing the entry of contaminants. Additionally, it is possible to recycle the steam from sterilization processes by injecting it in the fruiting room. The fruiting room is kept at a relative negative pressure, in order not to disperse mushroom and contaminants spores in the rest of the farm/lab. For example, see on the picture ofthe article on our two setups,the airflow crossing each room, indicated by arrows.

2. Mushroom Farm Components

The farm components mentioned by Stamets apply to all scales. Small home scale projects have similar components than industrial-scale huge projects but use very different equipment (see equipment page). These components are the following :

1. Preparation space : this is where the substrate is prepared, weighted, watered, mixed, sometimes bagged. It may include the sterilization as well, that Stamets calls Boiler room or Pasteurization room. If you work at home, this is typically done in the kitchen. If you make a small farm, this will look like a kitchen: sink, stove, pressure cooker, table, etc.

2. Lab – Sterile inoculation room:is the cleanest room, used for inoculation on front of a HEPA flow hood or inside a glovebox. Typically this room is air-tight positively pressured with a HEPA filtered clean air. This room may include the incubation space in the same room.If you work at home, you may choose the more contaminant free room, e.g. living room, bedroom, office (no kitchen, no bathroom, no plants around). If you make a small farm, this may look like a closed clean room with hepa filtered ventilation. See more details on sterile room design later on this page.
3. Incubation space:Sometimes inside the sterile room, a natural extension of it. After inoculation, the blocks require space on a shelf in a clean room. It is a critical phase until the mycelium takes hold of the substrate. They need a little ventilation and no light. At home, incubation can be in the same room than inoculation, preferably in a closed but not air tight closet. At small farm scale, a closed room with shelves and controlled ventilation may be needed.
4. Fruiting room:The block is moved into the fruiting room when it is ready to fruit. The room is ventilated and humidified about 80%, sometimes heated or cooled. It must provide sufficient natural or artificial light for the mushroom species. The walls and floor must withstand moisture, and be easy to clean. At home, typically this is the basem*nt, as it has sufficient light and a natural good temperature and moisture. A ventilator and a humidifier are used to condition the environment. Shelves are used to place the blocks. See more details on fruiting room design later on this page.

Fruiting Room Example 1: In our growing space, we ventilate our 4x5m fruiting room with 2x Rucks 150L (770m3/h) ventilators 1/4 of the time. We humidify with an InkBird humidistat ,2x 3 cell ultrasound humidifiers, and a 12cm extractor fan. We recirculate with multiple 15-25cm fans. See this setup video.

Fruiting RoomExample 2: Mossy Creek Mushrooms blog has an article describing their growing space. They explain how they control air, light, humidity and their original and inexpensive shelfing system.

In addition, a commercial grower will probably require also these components :

1. 1. Relaxation :Because growing things can be hard work on your body, a comfortable resting space with music and couch was always included in our projects. It’s a also a good place for mushroom growing books, and possibly an office corner to write, etc.

1. 1. Storage space :You may have a lot of substrates to store waiting to process. Straw takes a lot of space. There is other things to store as well : sawdust, grain, bran, gypsum, lime, etc. All these are dusty and may attract insects: airtight barrels advised. Organize the storage to be regularly inspectedfor presence of insects, mold, etc.

1. 1. DIY corner:If you are going to build from scratch many things like we do, a dedicated DIY corner is a good addition to the farm: to store all the tools, a table to work on it, and consistent storage space for recycling materials.

1. 1. Product Storage:Depending on your scale, storing fresh mushrooms can become a problem if you are not prepared for it. Mushroom takes space to store, i.e. 10L per kg of clustered mushrooms. At home, you may find an extra fridge handful. At small scale, one or two large fridges can suffice. At a bigger scale, it’s worth building a walk in rather than taking more fridges.
      Fridges require continuous monitoring as they may get out of balance when too full, poorly ventilated, too empty, or opened too often. You want to avoid that the mushrooms freeze, get wet or slowly dry.
      Be prepared also to transform your product, from canning with vinegar in glass jars to drying mushrooms. They store a long time like that room temperature, but still benefit from cooling. Dry mushrooms are best kept in deep freeze.

1. 1. Outdoor preparation :While some aspects of mushroom cultivation are ultra clean and sterile, others are very dirty and dusty. You may need exterior space for those. One of the worst jobs is to chip the straw yourself (see our video). Other dirty/dusty works may include DIY works, transferring straw, sawdust, grain in bulk, etc. You may want to protect yourself with a mask.It is best for your lab to move a maximum of these activities outdoor.

1. Outdoor recapture:If you have space and time, you can make an outdoor recapture space where you move the blocks after 1-3 harvest in the fruiting chamber. They will continue producing at a lower rate, with a higher contamination rate. This space won’t be as productive but will provide extra mushrooms for free. Later on, when the block is completely dry or overcome with contaminants, it can be composted. At home, the recapture space can be a shade house in the garden, where the block spends some time, before being used on the soil as mulch on in the compost. As small scale farm, we donate our used blocks to gardens and people to learn and experiment, get some mushrooms before composting them.

3. Spawn Lab Sterile Room

4. Fruiting Room